/*
 * Copyright (c) 2011, Yawning <yawninglol at gmail.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   * Neither the name of the Mew Developers nor the
 *     names of its contributors may be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

package yawning.mew.GeneticOptimizer;

import org.apache.commons.math.genetics.Chromosome;
import org.apache.commons.math.genetics.Population;
import org.apache.commons.math.genetics.StoppingCondition;

public class GOStoppingCondition implements StoppingCondition {
	private int mGenerations;
	private int mStopAt;
	private Optimizer mOptimizer;
	private int mStagnationCounter;
	private double mLastFitness;

	public GOStoppingCondition(Optimizer opt, int generations) {
		mOptimizer = opt;
		mStopAt = generations;
	}

	@Override
	public boolean isSatisfied(Population population) {
		mGenerations++;
		GOChromosome best = (GOChromosome) population.getFittestChromosome();
		mOptimizer.mPopulation = population;	// Store a reference to our last generation's population so we can use it as a fitness value cache.

		// Debugging
		StringBuilder s = new StringBuilder();
		s.append("Generation: ").append(mGenerations).append(' ');
		s.append(best.toString()).append('\n');
		if (mGenerations % 10 == 0) {
			s.append('\n');
			for (Chromosome chromo : population) {
				GOChromosome chromosome = (GOChromosome) chromo;
				s.append(chromosome.toString()).append('\n');
			}
		}
		System.out.print(s.toString());

		if (mGenerations == mStopAt) return true;

		// Try to detect stagnation and terminate early.
		double f = best.getFitness();
		if (f == mLastFitness) {
			mStagnationCounter++;
		} else {
			mStagnationCounter = 0;
		}
		mLastFitness = f;
		if (mStagnationCounter > 0 && mStagnationCounter == mOptimizer.mStagnationHalt) return true;

		return false;
	}
}
